Ok, let's walk through this and see if we can shine some light...
There is a problem if you're logged into the processor and under some conditions if you don't log out but disconnect, the processor will no longer communicate. I have no idea if this is part of the problem with the Ecoms.
What do you mean "logged into" and "don't log out but disconnect"? The protocols that the ECOM uses with a DirectLogic PLC are generally connectionless. There is no login or logout, unless you are talking about entering a password. Modbus/TCP has TCP connections, which are actual end-to-end connections, and if you drop the connection without going through the proper TCP disconnect sequence, the connection will stay open until it times out...and TCP timeouts can be fairly long. They do timeout eventually though, and we do have inactivity timeouts where eventually we dump connections that aren't being used so they can be reused. But please help me understand.
I do know that I have a bunch of them that will randomly stop communicating to the processor, but are still on the network. As there are no status bits, words, or anything else to indicate what the problem was, is, or might be, its rather difficult to diagnose or correct.
We have on many occasions built custom firmware with diagnostic code built in. We can also learn a great deal from Wireshark traces. If you are serious about solving this, then please work with us.
I can understand faulted communications packets, incomplete transfers, etc. I can't fathom any system in this kind of environment that would be developed to simply have no timeouts, resets, etc. so the system can recover, or attempt to. This apparently is a one shot deal. Its either ok, or cycle power.
Again, you seem to be assuming...wrongly...that the system is built without fail-safes. I assure you that is not true in the case of the ECOM. If the PLC itself is going on walkabout...and it may be...we need to address that with Koyo and ADC, and we will. We first have to duplicate the problem, document the issue, and then raise Cain. We will need you to work with us on that though.
Not exactly what I can tell my customer since its not a once in a year thing but happens at least every day or two. And I can test every switch, cable and connector, and place filters on every incoming power line. Still doesn't tell me why the Ecoms can't communicate.
Not trying to pick or maintain a fight, but you seem pretty stuck about the fact that the ECOM isn't communicating, rather than focusing on helping us change that. It may be the ECOM, it may be the PLC, and both can be fixed. There may also be a workaround, once we understand what is happening.
You have a choice: 1) Rip it all out and return it, or 2) Help us help you. I would prefer #2, but that has to start with you moving on from 'I can't see why it doesn't work' to 'What do I need to do to help you help me?' I am sorry if ADC Tech Support was not able to help you. We can, but haven't heard a peep about this until yesterday. Please give me the courtesy of at least a few business days to help you...when I actually have some staff in the building.